Loss in activity and catalyst recyclability in batch and continuous supported atom transfer radical polymerization

Cu¹Br/HMTETA physically adsorbed to silica-gel is used in batch and continuous ATRP processes to study the loss in catalyst activity with catalyst reuse. The loss in catalyst activity cannot be attributed to an oxidation of the catalyst as the catalyst is found to be fully regenerated by an addition of fresh ligand. The primary location for catalytic activity is found to be in solution and it is the loss of these soluble species that account for the loss in activity. A partitioning equilibrium of the active catalyst species between the support's surface and the solution accounts for the recyclability of the catalyst and the differences in process performance. © 2006 American Chemical Society.